: The objective of the program is to develop a 90-day injectable microcapsule form of estradiol to be used for estrogen replacement therapy in postmenopausal women. During Phase I, BIOTEK used the new spray-core microfluidized bed process to prepare estradiol loaded microcapsules and demonstrated sustained 90-day delivery from such capsules in rabbits and in rats. During Phase II, microcapsule development will be completed; all preclinical studies required by the FDA will be conducted; manufacturing specifications, processes and controls will be documented, IND application will be filed with the FDA; microcapsules for clinical studies will be manufactured and a clinical study of safety and pharmacokinetics will be conducted.